PGA4 and cancer: According to marker genes cancer cells (expressing CLDN4, REG4, TTF3, and CEACAM6), mucous cells (expressing TFF1, MUC5AC, TFF2, and MUC6), chief cells (expressing PGA3 and PGA4), parietal cells (expressing ATP4A and ATP4B), and endocrine cells (expressing CHGA and CHGB)19 (Fig. 2b), the subclusters were redivided into 5 subclusters.